The Universal Definition of Myocardial Infarction (acute myocardial infarction [AMI]) requires detection of increasing or decreasing cardiac biomarkers (preferably cardiac troponin) with >or=1 value >99(th) percentile, together with either clinical symptoms, new ischemic electrocardiographic changes, or typical imaging findings indicative of myocardial necrosis as diagnostic criteria for AMI. However, a small cardiac troponin elevation together with ST-T segment abnormalities may also occur in clinically stable populations. Accordingly, 0.6% of elderly subjects from a community sample (PIVUS Study) and 6.7% of patients stabilized after an acute coronary syndrome (FRISC II Study) would have been labeled AMI following the Universal Definition of AMI when diagnostic classification had been based on a single cardiac troponin I result. In conclusion, our results emphasized the importance of a significant change in cardiac troponin to avoid misdiagnosis of AMI.